1. Field of the Invention
The present invention relates to an electronic image pickup apparatus for photographing a still picture.
2. Description of the Related Art
As a solid state image pickup device suitable for an electronic still camera, for example, a CCD image pickup device, a square-lattice all-pixel reading type device has been proposed. In the square-lattice type image pickup device, the vertical intervals of adjacent pixels accord with the horizontal intervals thereof. For example, the square-lattice type image pickup device is used for matching a picture signal with a monitor of a personal computer. Since a CCD image pickup device for use with a conventional video camera or the like generates an interlaced output signal, as shown in FIG. 12, the device stores the signal for 1/60 seconds (one field), reads two pixels, mixes two pixels read by a vertical transferring CCD, and shifts the vertical positions of pixels to be mixed depending on whether the current field is an odd field or an even field so as to accomplish the interlace scanning operation.
With the CCD image pickup device that reads a signal corresponding to the NTSC system or the PAL system, while the user is watching a picture read from the CCD image pickup device and a background picture, a composite picture thereof is created corresponding to a key (chroma) signal. The composite picture displayed on the monitor is printed by a printer. Since picture data corresponding to the NTSC system or the PAL system is printed, the picture quality including resolution is limited.
Since the above-described CCD image pickup device stores a signal for 1/60 seconds, it can properly photograph a moving picture in comparison with a frame storing system for storing a signal for 1/30 seconds. However, the vertical resolution of the CCD image pickup device is inferior to that of the frame storing system. Thus, the CCD image pickup device is not suitable for an image pickup device for use with an electronic still camera. To solve such a problem, an all-pixel reading system for storing a signal for 1/30 seconds and reading all pixels has been proposed. According to this system, although the vertical resolution can be prevented from deteriorating, to output a captured picture signal from the image pickup device, when the number of pixels and the read clock are the same, the device according to such a system requires twice that of the above-described image pickup device for the video camera. More reality, in the system, a captured picture signal is generated at intervals of 1/30 seconds.
The above-described read time is applicable for an image pickup device with effective pixels of 480 (vertical).times.640 (horizontal). Thus, a professional type device requires a higher resolution than such a home-use image pickup device. For example, a high resolution CCD image pickup device with effective pixels of 1024.times.1280 is used. In this case, the read time becomes long. When all pixels of one picture are read, it takes for example 1/12 seconds. With such a picture, as a method for improving the picture quality of the composite picture, a computer can be used. In this method, a picture is captured and processed by the computer so as to create a composite picture.
With the computer, the picture quality of the composite picture can be improved. However, in this method, to check the angle of view and so forth, each captured picture should be transferred from the electronic still camera to the computer so as to check the composite picture of the captured picture and the background picture. With the high resolution CCD image pickup device, since the data amount is very large, it takes a long time to transfer data.